There is a known endoscope including two bending sections disposed at the distal end of an insertion part and adjacent to each other in the longitudinal direction (see, for example, patent literature PTL 1 below). This endoscope allows the observation and treatment of an affected area located toward the front in the insertion direction. Also known is an endoscope having a U-shaped bend at the distal end of an insertion part (see, for example, patent literature PTL 2 below).
However, when used for treatment in the lumen of an organ such as the large intestine, the above endoscopes in PTLs 1 and 2 present a problem in that an affected area located in front of, behind, or across a fold on the inner wall of the lumen in the insertion direction cannot be sufficiently treated.